The basic principle of weight gain is simple: You need to consume more calories than you expend. Here are a few tips to do just that!

1. Eat more calories
This involves some calculation. The approximate normal daily caloric requirement for an average male who performs light activity is 2,200; for a female, it is 1,900.You need to eat around 1,000 extra calories per day to gain less than half a kilo a week.

2. Make smart choices
For example, choose dairy products, fish and meat over bread. Choose eggs over vegetables. Eat foods with high protein content such as beans, pulses and peas, and foods with high starch content such as potatoes, rice and tapioca.

3. Protein is important
Increase your protein intake. Your body needs a lot of protein to build new muscle. But since most of the calories for weight gain comes from carbohydrates and fats, do not replace them with protein.

5. Drink More Fluids
Drink a lot of fluids that supply nutrients and calories; milk, fresh fruit juices and energy drinks are good examples.

6. Intensify Workouts
Aerobics are great, right? Not for weight gain!
You need to exercise really hard and intensely to gain muscle mass.

7. Weights are the way to go
Focus on free weight exercises (which do not require machinery) that target your large muscle groups. For example, you need dumbells, not fancy gym machines. Free weights put the most stress on muscles and stimulate the maximum number of muscle fibres.

The best weight training exercises for building muscle mass are free weight exercises like squats, dead lifts, bench presses, barbell rows, pull ups and bar dips. These exercises are best done under supervision, but they don't need machinery.

8. Space out your workouts
If you have a high basic metabolic rate -- which means you expend a lot of energy even at rest -- you need short intense workouts instead of long periods of low-stress activity.